1. Field of the Invention
The invention is directed to a manipulative laboratory device. More particularly, the invention is a laboratory apparatus which includes means for separating a constituent. In still greater particularity, the invention is an apparatus for retaining and washing a plurality of objects. By way of further characterization, but not by way of limitation thereto, the invention is a device which is attachable to a test tube rack and in which a plurality of beads may be contained and washed after having been separated from the test tubes.
2. Description of the Prior Art
In an immunochemical assay, an object such as a plastic bead is coated with an immuno reactant such as an antibody or antigen. The bead is added to a sample containing the complementary antibody or antigen to be assayed. If present, the immuno reactant in the sample will react with the affixed immuno reactant and thereby adhere to the bead. A reagent containing a known quantity of one of the immuno reactants which has been labeled with a detectable member such as an enzyme, radioisotope or fluorescent moiety can then be added to react with one of the reactants on the bead. The bead can then be separated from the reaction medium and examined to determine the presence or absence of labeled reagent.
The separation of the bead from the reaction medium can be accomplished in a number of ways. One method involves aspirating the liquid phase from the reaction vessel. Another method involves carefully decanting the liquid, and still another involves using a reaction container with a crimped or constricted orifice to retain the object while allowing the liquid phase to be poured off.
A method and apparatus for washing beads in test tubes is disclosed in U.S. Pat. No. 4,284,603 issued on Aug. 18, 1981 to G. K. Korom. The device disclosed therein includes a test tube rack for vertically aligning a plurality of test tubes which can contain the bead and liquid phase of the reaction. The tops of the test tubes are covered with a porous retaining means. This retaining means keeps the test tubes in the rack and the beads in the test tubes. The retaining means is held in place by side portions which engage the sides of the test tube rack. The entire apparatus may be inverted and the liquid contents may be removed from the tubes while retaining the objects within the tubes. This apparatus allows liquid to be poured off from the test tube while retaining the solid object, or bead, within the test tubes.
While suitable for its intended purpose, the above described device uses a restrictive screen over the open end of the test tubes to retain the beads in the tubes. The device thereby produces slow water flow requiring vigorous shaking of the inverted rack to remove the washing liquid from the tubes. A number of washing cycles may be required in order to completely wash the beads within the tubes. In addition, because the test tubes are preferably disposed of after washing, this device unnecessarily requires the washing of test tubes which is not necessary. The device is thus cumbersome, difficult, and time comsuming to use, and requires repeated washing cycles to completely wash the beads.